1. Field of the Invention
The present invention relates to an electronic calculator adapted for displaying a graph obtained by processing graphic data input by calculation and graphing the result of calculation.
2. Description of the Prior Art
Electronic calculators are disclosed, for example, in U.S. Pat. Nos. 4,208,720, and 4,603,396, and 4,609,918. Also proposed are electronic calculators having a graph displaying function which includes a combination of such disclosed calculators. Such a calculator heretofore proposed and adapted for graphing an input functional equation and displaying the graph on a screen is provided with a phantom screen (buffer) on each of its upper and lower sides and the opposite lateral sides for displaying the remaining portion of the graph other than the portion thereof shown on the display screen. Thereby, the remaining portion of the graph on the phantom screen is shown on the display screen by operating a cursor.
However, the conventional calculator of the the type described has the problem of being unable to display the graph in its entirety since only one screen area of the remaining graph portion can be displaced with respect to each of the upward, downward and opposite lateral directions. To overcome this problem, it appears useful to prepare a multiplicity of phantom screens (buffers), but providing this multiplicity of screens results in a drawback of necessitating a memory of great capacity and increasing the cost.